The present invention relates to stringed-instrument fretboard capos, and more specifically to guitar and banjo capos that are easy to clip-on and remove, and that protect the instrument fretboard from being damaged during its installation and removal.
Capotastos are used by musicians who play guitars and banjos to make it easier to change music keys. In effect, a xe2x80x9ccapoxe2x80x9d will simultaneously finger all the strings at a single fret as long as the capo is secured in place. This therefore sets the half-notes sounded when the open strings are strummed. Playing the guitar, banjo, or lute, is therefore highly simplified without compromising the original composition. Capos are in widespread use as a result, and there are many screw-down and clamp-down versions being sold commercially.
One particular type of capo is a levered clamp with separate rubber linings on the inside of the two jaws, commonly called a xe2x80x9cC-clampxe2x80x9d capo. Richard Shubb describes such a capo in U.S. Pat. No. 4,250,790, issued Feb. 17, 1981, (Shubb ""790). A frame with a straight rubber facing is clamped down tight over the strings of a guitar and pulls them against the fretboard. An idler clamp with a concave curve and a short rubber facing presses from behind the fretbbard. A locking lever with a setscrew rides over a hump on the back of the idler clamp and is able to lock the idler clamp tight. The setscrew allows for some adjustment of the pressure and allows a range of fretboard thicknesses to be accommodated. The placement of the rubber linings allows the fretboard to be marred by exposed metal in the capo. And the setscrew tends to gouge the backside of the idler clamp such that the action is no longer very smooth. Experience has shown that the commercial units sold like this also tend to pull away from the strings. Such capo was improved by Richard Shubb, and is described by him in U.S. Pat. No. 5,792,969, issued Aug. 11, 1998, (Shubb ""969). The basic form is maintained from Shubb ""790, but an idler wheel is provided between the setscrew end and the backside of the idler clamp to relieve friction and gouging when the clamp is locked. A large knurled head is shown on the outside end of the setscrew to make it easier for the user to adjust the clamping range. Shubb ""969 shows the rubber facing on the xe2x80x9ctop arm 7xe2x80x9d as fully wrapping around the distal end. There is still a large exposed metal area inside the jaws, e.g., around the xe2x80x9croll pin 39xe2x80x9d, that can contact and mar the users"" fretboards.
A different approach to locking a capo down on a fretboard is described by Richard Steinberger in U.S. Pat. No. 6,008,441, issued Dec. 28, 1999. The idler clamp is fitted with a spring that presses the jaws closed around the fretboard. A release lever is linked to force the idler clamp jaws open when it is squeezed together by hand with a stationary lever on the frame. A problem with prior art xe2x80x9cC-clampxe2x80x9d type capos is that they tend to move across the strings and pull them out of tune, especially when being clamped on. There is a slight decrease in the applied pressure when the adjustment tip rotates past its top-dead-center and comes back in a bit. Such xe2x80x9coverstretched knee effectxe2x80x9d seems to be inherent in conventional capos.
An object of the present invention is to provide a capo that grips the fretboard and strings firmly.
Another object of the present invention is to provide a capo that will not mar a fretboard.
A further object of the present invention is to provide a capo with a positioning bumper that ensures consistent positioning against the fretboard.
Briefly, a capo embodiment of the present invention comprises a string press for clamping down on the strings of a string-instrument against a front side of a fretboard. An extension arm curves behind and has an idler clamp with a first pivot attachment. Such enables a clamping action against a backside of the fretboard. A continuous insert having a positioning bumper maybe disposed all along an inside surface of the string press from a distal end across the first pivot attachment bridging over to an inside surface of the idler clamp and out to its distal end. The positioning bumper may also be on an insert disposed on the inside surface of the string press or on the inside surface of the idler clamp. A locking lever has a second pivot attachment to the extension arm behind the first pivot attachment. It provides a locking action against a backside of the idler clamp. A setscrew disposed in the locking lever provides an adjustable locking action between the idler clamp and the locking lever, e.g., for a range of thicknesses of the fretboard to be accommodated. A plastic, pointed tip on a distal end of the setscrew helps for a smooth engagement along a backside of the idler clamp. A grooved slot in the backside of the idler clamp provides a track in which the plastic, pointed tip of the setscrew is smoothly guided into a locking position. A depression located at a locking end of the grooved slot provides for a detent in the locking position.
An advantage of the present invention is that a capo is provided that grips the fretboard and strings firmly without detuning the instrument.
Another advantage of the present invention is that a capo is provided that will ensure consistent positioning against the fretboard.
A further advantage of the present invention is that a capo is provided that is simple to use.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment as illustrated in the drawing figures.